How to set a message breakpoint at a subcontrol in a ATL control?

There is a program whose GUI is a ATL dialog. Now, i wanna set a message breakpoint(WM_LBUTTONUP) on its subcontrol. But i can oly get the main dialog's ID using HwndSpy. So, i don't know how to set such a breakpoint. I use OllyDbg. Any idea?